Equipment for treating materials at high temperature and at high pressure

ABSTRACT

In a device for treating material at high temperature and high pressure which includes a high pressure cylinder built from a tube and a prestressed, force-absorbing wire or strip sheath wound around the tube, with end closures projecting into the cylinder and a press stand for holding the end closures, the cylinder is provided with longitudinally extending cooling channels either running along the inner wall of the sheath or at an intermediate position within the sheath, adjacent to the inner wall thereof.

United States Patent Elmgren et a].

[ Aug. 19, 1975 EQUIPMENT FOR TREATING MATERIALS AT HIGH TEMPERATURE AND AT HIGH PRESSURE Inventors: Staffan Elmgren; Lennart Svensson,

both of Helsingborg, Sweden Allmanna Svenska Elektriska Aktiebolaget, Vasteras, Sweden Filed: July 16, 1974 Appl. No.: 488,991

[73] Assignee:

[30] Foreign Application Priority Data May 7, 1974 Sweden 7406059 US. Cl. 266/5 E; 425/78 Int. Cl. C21D l/00 Field of Search 75/22l, 226; 266/5 R, 5 E,

266/24; 425/DIG. 26, 77, 78

[56] References Cited UNITED STATES PATENTS 3,676,079 7 1972 Morgan 75/226 x 3,703,278 11/1972 lsaksson 266/5 E x Primary Examiiier-Gerald A. Dost [57] ABSTRACT sheath or at an intermediate position within the sheath, adjacent to the inner wall thereof.

6 Claims, 4 Drawing Figures PATENTEUAUB-I 9:975 Y 3,900,189 sumlufz 6 Fig/ PATENTED M181 9 I975 sum 2 o 2 Fig. 2

EQUIPMENT FOR TREATING MATERIALS AT HIGH TEMPERATURE AND AT HIGH PRESSURE BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to equipment for treating materials at high temperature and high pressure, comprising a high-pressure cylinder which is built up of an inner thick-walled tube and a prestressed wire or strip sheath wound around said tube and taking up the main part of the stresses occurring, end closures projecting into the cylinder, which together with the cylinder form a pressure chamber, and means for taking up axial compressive forces from a pressure medium enclosed in the pressure chamber. The equipment is primarily intended for pressure furnaces for hot pressing of, for example, powder bodies at high temperature, up to I500C, in a gaseous atmosphere under high pressure, preferably 500 bar and thereabove, for bonding the powder grains into a solid homogeneous body having high density.

2. The Prior Art Furnaces of this kind have been further described in US. Pat. No. 3,628,779. The pressure chamber surrounds a furnace compartment. Between the furnace compartment and the walls of the pressure chamber is an insulating casing. The structure which provides the space inside the pressure chamber is expensive, so it is desirable to hold down the wall-thickness of the insulation to obtain a large useful furnace space. Because of the heat losses through the insulating sheath the walls of the pressure chamber are heated. In view of the high stresses in the high-pressure cylinder, the temperature of the material must be limited to some hundreds of degrees Centigrade.

Up to now stripor wire-sheathed high pressure cylinders have been cooled on the outside. Particularly in high-pressure cylinders of great inner diameter and intended for high pressure, the strip or wire sheath will be thick and the temperature difference between the inner surface of the cylinder and the outer, cooled surface of the strip sheath will be great, often 50 100C. To be able to keep the inner temperature below the allowed level a great quantity of cooling water and/or low temperature of the cooling water is required. In some cases it may involve insurmountable difficulties to keep the cylinder temperature below the necessary level. The temperature gradient within the strip sheath is unfavorable from the point of view of strength. The distribution of stresses within the strip sheath is influenced in dependence on the temperature gradient, which affects the strength. This influence must be taken into account when calculating the strength and determining the allowed stress.

SUMMARY OF THE INVENTION According to the invention, the high-pressure cylinder is provided with cooling channels in a tubular layer in the strip sheath, or between the strip sheath and the inner tube of the cylinder.

In a preferred embodiment of the invention, a layer of rods with bevelled corners are laid around the inner tube of the high-pressure cylinder, thus obtaining a tubular rod layer. The cooling channels are formed between the bevels of the rods and the surrounding strip sheath or a sheet-metal tube which prevents cooling medium from penetrating into the strip sheath of the cylinder. The rods are parallel with the axis of the cylinder. Thus, the cooling channels are axially oriented. Cooling agent is supplied through end rings and is distributed around the cylinder through an annular space formed by the end rings and the rods. The rods suitably cover the outer surface of the highpressure cylinder entirely. The radial forces in the strip sheath will then be substantially evenly distributed and additional stresses are substantially avoided. However, from the point of view of strength it may be suitable to locate the tubular rod layer between two layers of strip in the sheath, in view of the extremely great stresses in the inner tube of the high-pressure cylinder, in order to eliminate entirely the risks of local stress concentrations in the inner tube of the high-pressure cylinder.

In an alternative embodiment, a tube with slots is placed around the inner tube of the high-pressure cylinder and the cooling channels are formed by the walls in the slots and preferably by the surrounding strip sheath or a sheet-metal tube between the tube with the slots and the strip sheath. Cooling medium slots on the inside of the tube may be used in certain cases but may involve a certain risk of dangerous stress concentrations in high-pressure cylinders, the inner tube of which is greatly stressed and made of a highstrength material which is often sensitive to stress concentrations.

In the two embodiments therefore, the cooling channels are in heat exchange contact on at least one side with the strip, and are located at a position at a substantial distance inwardly from the outside of the strip.

BRIEF DESCRIPTION OF THE DRAWINGS Equipment constructed according to the invention is described more fully with reference to the accompanying drawings.

FIG. I shows a highpressure furnace, partly in section.

FIG. 2 is an axial section through the upper and lower ends of a high-pressure cylinder.

FIG. 3 is a radial section through the same highpressure cylinder on the line AA in FIG. 2, and

FIG. 4 is a radial section through an alternative form of cylinder.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the drawings, 1 designates a press stand which is movably arranged between the position shown in FIG. 1 and a position where it surrounds the pressure chamber 2. The press stand is of the type which consists of yokes 3 and 4 and intermediate spacing pieces 5 and a prestressed strip sheath 6 holding these together. The stand is supported by wheels 7 running on rails 8. The high-pressure chamber 2 is supported by a pillar 9. It comprises a highpressure cylinder 10 having an upper end closure 11 with a seal 12 and a lower end closure 13 consisting of a ring 14 with a seal 15 and a bottom portion 16 with a seal 17 projecting into said ring. In the pressure chamber 2 is a furnace space 18 with a workpiece 49. The pressure medium forces acting on the end closures 11 and 13 are taken up by the press stand 1. Between the walls of the pressure chamber and the furnace room 18 is an insulating casing consisting of an insulating cylinder 19, an insulating lid 20 and an insulating bottom 21. The furnace room is surrounded by electrical heating elements 22. These are supplied with energy through the line 23. Pressure medium is introduced into the pressure chamber 18 through the channel 24. The bottom portion 18 is raisable and low erable for charging the furnace room. It is supported by a bracket 25 with a guide 26 running along a rod 27. The operation is performed with the help of a hydraulic cylinder 28, the piston rod of which, 29, is connected to the guide 26.

The high-pressure cylinder contains an inner tube 30 around which there is wound a strip sheath 31. The strip is wound on under prestressing. The strip sheath absorbs the main part of the forces generated by the pressure medium. Previously, in pressure chambers with strip-wound high-pressure cylinders, the. strip sheath was cooled on the outside in order to limit the temperature on the inner wall 32 of the tube 30 to a value tolerable from the point of view of strength. As the pressure and the diameter of the cylinder increase, the thickness of the strip sheath increases, and also the difficulties of keeping the temperature of the tube wall down. In case of great thicknesses the temperature drop between the tube wall and the outer portion of the strip sheath will be considerable during the heat transfer in question and may amount to 50 100C. Further, the temperature gradient within the strip sheath causes undesirable changes in the stresses within the dfferent layers of the strip which are both unfavorable and difficult to calculate.

To avoid the drawbacks, in the present designs cooling channels are located inside the strip sheath or be tween the strip sheath and the inner tube of the cylinder. In the high-pressure cylinder according to FIGS. 2 and 3, a number of rods 33 have been inserted between the tube 30 and the strip sheath 3]. These rods are axially oriented and form an annular layer around the tube 30. The inner surfaces 34 of the rods make contact with the outer surface 35 of the tube 30. The outer corners of the rods are bevelled. Between the rods and the strip sheath 31 is a sheet-metal tube 36. The bevelled surfaces 37 of the rods and the'inner surface 38 of the sheet-metal tube together form the walls of axial channels 39. At the ends of the high-pressure cylinder there are end rings 40 which are axially fixed in relation to the tube 30 with lock rings 41. Between the tube 30, the end rings 40 and the rings'42 there is formed an annular slot, in which there is inserted a sealing ring 43 preventing cooling medium from penetrating out between the tube 30 and the rings 40. Between the tube 30 and the rings 40 there is a sealing ring 44 preventing pressure medium from penetrating out into the strip sheath. In the rings 40 is an annular space 45 for distribution of cooling medium around the rods 33.

Radialchannels 46 lead to the channels 45. Cooling medium is introduced through the channel 46 in the ring and is distributed in the annular space around the rods 33 and flows axially in the channels 38 to the space 45 in the other ring 40 and from there through the channel 46 and 'lines (not shown) to an outflow or to a cooler.

FIG. 4 shows an alternative embodiment having rods located between layers inside the strip sheath. The strip sheath consists of an inner portion 31a which is directly wound around the tube 30. This part consists of a small number of strip layers, for example between three and 10 layers. Outside the inner portion 31a of the strip sheath there are placed a number of rectangular rods 50 at a distance from each other. Outside the rod layer the outer portion 31b of the strip sheath is wound. Between the rods 50 and the strip sheath portions 31a and 3112 there are formed axial cooling water channels 51. The inner strip sheath portion distributes the rod pressure so that the tube 30 subjected to a substantially uniform radial force.

1. Equipment for treating material at high temperature and high pressure'comprising a high pressure cyl- -inder which is built upfrom a tube and a prestressed force-absorbing wire orstrip sheath, wound around said tube, end closuresprojecting into the cylinder and means for taking up forces acting on the end closures, the cylinder is provided with cooling channels in a tubular layer in heat-exchange contact on at least one side with a part of the strip sheath and located at a substantial distance inwardly from the outside of the strip sheath.

2. Equipment according to claim 1, in which the layer of cooling channels is in heat-exchange contact with the inner surface of the strip.

3. Equipment according to claim 1, in which the layer of cooling channels is located within the main body of the strip. v

4. Equipment according to claim 1, in which axially arranged rods form the cooling channels.

5. Equipment according to claim 4, in which the corners of the rods are bevelled and the axial cooling channels are formed between said bevelled corners and at least one element on one side of the layer of rods.

6. Equipment according to claim 5, in which such element is a sheetmetal tube on the outside of the rods. 

1. Equipment for treating material at high temperature and high pressure comprising a high pressure cylinder which is built up from a tube and a prestressed force-absorbing wire or strip sheath, wound around said tube, end closures projecting into the cylinder and means for taking up forces acting on the end closures, the cylinder is provided with cooling channels in a tubular layer in heat-exchange contact on at least one side with a part of the strip sheath and located at a substantial distance inwardly from the outside of the strip sheath.
 2. Equipment according to claim 1, in which the layer of cooling channels is in heat-exchange contact with the inner surface of the strip.
 3. Equipment according to claim 1, in which the layer of cooling channels is located within the main body of the strip.
 4. Equipment according to claim 1, in which axially arranged rods form the cooling channels.
 5. Equipment according to claim 4, in which the corners of the rods are bevelled and the axial cooling channels are formed between said bevelled corners and at least one element on one side of the layer of rods.
 6. Equipment according to claim 5, in which such element is a sheetmetal tube on the outside of the rods. 